GENEVA — More than 100 trucks laden with emergency food and medicine began deliveries on Wednesday to tens of thousands of desperate Syrians in five locations besieged for months by the civil war, United Nations officials and relief workers reported.

The deliveries were the first significant aid to the afflicted civilians under a diplomatic arrangement negotiated during a meeting in Munich last week by the so-called International Syria Support Group of 17 nations and completed on Tuesday between the United Nations and the Syrian government, which had blocked access to the locations.

International aid agencies had loaded 115 trucks with food and medical supplies for 100,000 people in the western towns of Madaya and Zabadani, the northwestern towns of Fouaa and Kfarya, and the Damascus suburb of Moadhamiyeh. The trucks started moving in convoys on Wednesday and by evening three trucks had reached Zabadani, 24 trucks had entered Madaya and 13 had gone into Fouaa and Kfarya, relief workers and independent monitors said. They also said that aid had been delivered to Moadhamiyeh.

Video

As an aid convoy delivered food to the Damascus suburb of Moadhamiyeh on Wednesday, a resident described how families were managing to survive.CreditCreditLouai Beshara/Agence France-Presse — Getty Images

The convoy to Madaya was the first delivery in nearly a month to that town, where photographs of residents who starved to death have joined the list of iconic images of the five-year-old Syrian war. United Nations officials say ambulances of the Syrian Arab Red Crescent have made frequent visits and have evacuated some of the most urgent cases.

The Syrian Observatory for Human Rights, a Britain-based monitoring group with a network of activists in Syria, reported that a Syrian Arab Red Crescent delegation had entered Madaya early on Wednesday with a mobile clinic to treat residents who have been seriously wounded in bombings and other attacks.

The aid deliveries began as members of the International Syria Support Group, made up of countries closely involved in the Syrian conflict, including the United States and Russia, prepared to convene a meeting of its humanitarian task force in Geneva on Thursday to discuss expanding the aid deliveries to hundreds of thousands of people marooned in at least 15 besieged towns and inaccessible areas.

The group is seeking what it has described as a “cessation of hostilities” in the war to create the basis for a political settlement between President Bashar al-Assad and his adversaries, but there has been little indication that any of the antagonists or their backers are ready to halt fighting.

Video

For Syrians fleeing airstrikes in Aleppo Province and hoping to find refuge in Turkey, it remains to be seen what the recent cease-fire agreement means. Most of them are still stuck at the border.CreditCreditBulent Kilic/Agence France-Presse — Getty Images

If anything, Syrian forces and their Russian allies have intensified attacks in recent days, particularly in rebel-held parts of northern Syria, including the city of Aleppo, once the country’s commercial center.

On Monday at least four hospitals in northern Syria, including one run by Doctors Without Borders, were hit in aerial attacks that killed dozens of people, including children. The area is a focal point of bombing by Syrian and Russian forces. Russia denied responsibility, and Syria’s top diplomat at the United Nations said Doctors Without Borders should blame itself for having operated in his country without government permission.

The dangers of traveling in northern Syria were reflected Wednesday in a last-minute decision by United Nations officials to scrap for security reasons a planned visit to opposition-controlled areas of eastern Aleppo.

World Health Organization officials had received authorization from all parties for a trip to the eastern part of the city, which the United Nations has not visited for two years. But after setting out on the journey the team was instructed to turn back, Elizabeth Hoff, the W.H.O. representative in Syria, said by telephone.

A version of this article appears in print on , Section A, Page 10 of the New York edition with the headline: Syrians in Besieged Towns Are Starting to Receive Delayed Food and Medicine. Order Reprints | Today’s Paper | Subscribe